..an epithet given to any medicine adapted more to please than to benefit the patient - Quincy's Lexicon-Medicum Revised by R Hooper. London 1812

Historically, a pill with no active ingredients. The concept is sometimes extended to include more sophisticated sham 'interventions'. Therapy given to conscious patients has the potential for at least four effects:

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Placebo Effect

An observation that giving a placebo can produce reported improvements in symptoms despite the absence of active ingredients. Partly explained by the fact that many symptoms, for instance pain, are strongly modulated by psychological aspects so that fear and anxiety tend to accentuate pain.

Other similar effects include an observed efficacy of drugs depending on the colour.[1] Even the type of placebo can influence the size of the effect on the patient.[2]

The delivery of medical care is to do as much nothing as possible. - Samuel Shem in the House of God'

The art of medicine consists in amusing the patient while nature cures the disease. - Voltaire

Components of the Placebo Effect

It has been demonstrated that some of the factors contributing to the placebo effect can be separately analysed. This actually has produced results consistent with what is known of much of the art of medicine. Thus in one study the placebo of sham acupuncture produced a 16% improvement in adequate pain relief while the addition of a designed warmth, attention, and confidence building patient-practitioner relationship produced a further 18% gain
[4].

The correlation between bed side manner and placebo benefit might be postulated to help explain the known self selection process during medical training[5] as it is well known that specialities have a tendency to (self fulfilling) personality stereotypes[6]. Presumably an empathetic personality might be less necessary the stronger the evidence base for the biomedical components of usual therapy in a specialty. Thus areas of medicine with high cure rates might be attractive to personalities that found relying on empathy more challenging[7].

Size of placebo effect

The size of the placebo effect is related to the parameter evaluated. One early overview of 15 controlled trials suggested 35.2%[8]. In one study of the same stable asthmatics, that compared subjective improvement on visual analogue score, the improvement was 50% with salbutamol inhaler, 45% with placebo inhaler, 46% with sham acupuncture and 21% with no-intervention control (apart from interaction with study researchers). This study also showed that the objective measure FEV1 improved in 20.1% on the salbutamol but by only 7.3% in the other interventions[9].